Thursday, October 28, 2010

Man giveth and he taketh away

Man’s activities sometimes lead to extinction of other species. Of 10,000 bird species, 90 have been extinct since year 1600, another 1,000 are considered to be threatened. Of the extinct species, most were endemic, i.e. existed only in one isolated environment, mostly an island. A third of the extinct birds were on Hawaii. Also so called indigenous people exterminated other species. Twelve of the ninety bird species were exterminated by the Maori on New Zeeland, before arrival of the Europeans (NRM 2008). The Maori were also newcomers in the environment. The role of humans in the great death of big mammals in North and South America is still disputed, but the mammoth, the mastodon, camels, horses, bears and big cats disappeared within some thousand years after the first appearance of humans in the Americas. And there is no other, better, explanation given than that humans were to blame1. And it is sad. As Rolf says: “our life becomes poorer, emptier, when one life form is lost and diversity reduced. Life forms lost can never be replaced. A lost instrument is a loss for the whole orchestra, and reduced the power of the symphony” (Edberg 1976, my translation).

Meanwhile, we should have a reasonable perspective. Some claim that 99 percent of all species have been extinct already over the billions of . And most people are likely to be happy for that the Tyrannosaurus Rex is not roaming around; if it did I am certain that there would be calls for their culling. One often hear that there are chain reactions; if one species vanish there will be chain reactions so that other species also disappear, or that the whole balance in the ecosystem is disturbed with unpredictable consequences. And, for sure, it can be like that; there are keystone species. Perhaps it is a small predator that prevents a particular herbivorous species from eliminating dominant plant species. Without the predators, the herbivorous prey would explode in numbers, wipe out the dominant plants, and dramatically alter the character of the ecosystem. The scenario varies, but the central idea remains that one species has a fundamental impact on ecosystem functions. On the other hand, nature is very multifaceted, and at least in the longer view new balance will come. Also, species that vanishes are, mostly, specialists with narrow niches, rather than generalists. If they are gone, a generalist will often take their place, at least for a . Humans, mice and house sparrows are generalists which adapt themselves to many different environments (the mice and the sparrows seem to follow in our footsteps). Humans have, accordingly, taken over the role of many of the predators they have exterminated.

One hundred species per million are currently estimated to be lost per year (Rockström and others 2009). But what does it really say us? We have no clue even how many species there are: "Right now we can only guess that the correct answer for the total number of species worldwide lies between 2 and 100 million," says the ecologists Michael Rosenzweig (Society For Conservation Biology 2003). According to the latest Red List, 17 291 species out of 47 677 assessed are under threat: 21 per cent of all known mammals, 30 per cent of all known amphibians, 12 per cent of all known birds, 28 per cent of reptiles, 37 per cent of freshwater fishes, 70 per cent of plants, and 35 per cent of invertebrates (UNEP 2010b). Coral species are deteriorating most rapidly in status. Nearly a quarter of plant species are estimated to be threatened with extinction. The abundance of vertebrate species, based on assessed populations, fell by nearly a third on average between 1970 and 2006, and continues to fall globally, with especially severe declines in the tropics and among freshwater species (CBD 2010). Mass extinctions have taken place earlier. But the belief5 is that in earlier mass extinctions the rate was some 15-30 species per year while we are now speaking about thousands. According the Millennium Ecosystem Assessment is the rate some 50-1000 times higher than earlier. It estimates that the rate will increase further (MEA 2005).

We should be worried that so many species are disappearing in such a rapid pace. It can lead to a loss of potential raw materials e.g. for food, medicines or pest control agents. More than 50 percent of all medicines are produced by substances first detected in nature. More than 50,000 species are used for medical purposes of which 3,000 at a volume where they are traded internationally. Some 1,000 of them are grown commercially (Lehman 2009). But by and large it is not that one specie is lost that we shall see as a problem. If that would have been a disaster the world would already be gone as most species have been extinct. The problem is the large scale transformation of the whole planet to serve us humans, a process where we don’t only exterminate a few species, but landscapes, whole ecosystems and their essential life-upholding services. Measures to keep one species alive can command enormous resources, and ultimately, still be in vain because the habitat is simply not there any longer. Instead of straining the resources of society – and the support of the citizens – in order to save one species, it might be a better investment to put the resource into keeping some thirty other species, with better life expectancy so to say, abundant.

In the same way as we humans have created new ecosystems (farms, parks, rangelands) we have also created many new plants and animals. Just think about all dog races and the many cows and thousands of plants that don’t exist in nature. Many plants we grow can’t even multiply naturally (apples and roses just to mention a few). Of course, the plants we developed don’t replace the ones we exterminate. Now a lot of this agro-biodiversity is threatened. It might sound paradoxically that some of the most threatened plants, animals and ecosystems are those we created ourselves. But at a closer look it is quite apparent. We have created them and it is only our active care that keeps them alive. If we stop to use them and take care of them, their whole life space disappears. And we humans have constantly changed our use of nature as we have changed our own behaviours and our organization in society. As little as we can take care of every single species in nature, can we take care of every variety of cabbage or breed of sheep. Most of the things we created are not very competitive in nature and some of them are functionally defect, e.g. turkeys that can’t reproduce themselves or cows, like the Belgian blue, which can’t give birth naturally. And we have genetically modified crops which have the “evolutionary advantage” that the can survive a spray with a certain herbicide, glyphosate (better know under one of its trade names (Roundup ©). These crops are linked to an “ecosystem” where this herbicide is the main selective forces. There is certainly no value in keeping those genes alive!

Another peep view of Garden Earth

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